Such impact protection devices are able to significantly diminish the risk of injury of the vehicle occupant when the vehicle is involved in a side collision, as long as the gas bag is totally inflated before the occupant comes into contact with side parts of the vehicle body in a crash situation. Whilst the protection devices effective in a head-on collision need to be inflated within 30 to 60 ms for the driver and front passenger, this time is only 10 to 20 ms in the case of side air bags since the reaction travel is substantially shorter. Depending on the nature of the side collision and the design configuration of the vehicle body parts involved there is the risk of the gas bag getting caught in its deployment phase by side structural parts intruding into the vehicle passenger compartment thus preventing total inflation. Accordingly, the protective effect of the gas bag is diminished.